My original question was what was happening that made the profile transform not produce the published values.
You're expecting too much out of an image editing program designed for photographers who rely on visual judgement in determining what looks good to them. Exact numerical color matching is almost impossible to pull off by most photographers due mostly to the fact they have to rely on the limitations of their memory of the actual scene. Let me reemphasize the Eric Chan quote you posted...
They should be visually close, yes, at default ACR settings. (But not numerically close. The readouts in ACR are different from the readouts in DNG PE.)
If you want an exact visual match of your painting viewed on your display in ACR/LR to match the actual painting you see with your eyes, you're better off doing this using your eyes to guide your edits along with a custom camera profile. The main purpose of a camera profile using the DNG PE Wizard is to get the hues='a/b' Lab channel relationships to remain the same when applying contrast, brightness which in turn affect saturation levels. Human vision sees hue errors more so over any other of the HSL color channels which is why ACR/LR includes an HSL panel.
Believe me, it's easier than you think to get an accurate reproduction using ACR/LR. I've done it myself countless times photographing objects having a wide range of colors lit by various types of continuous lights, placed next to my display and editing to get an exact match. It's uncanny how close I get, but I have to use not just the profile but the HSL, WB sliders, SplitTone panel to get a match.
Sometimes I can just use Adobe Standard or ACR 4.4 default especially if I use neutral-ish fluorescent lights which I have several different brands. And due to these light's spiky spectra HSL panel and WB sliders really fix a lot of the hue errors.
This is why you need to shoot your paintings under full spectrum light source like Solux 4700K bulbs, strobes or flash. It will make editing a whole lot easier.